Variable bandwidth delayless subband algorithm for broadband active noise control system

Abstract

An active noise control (ANC) system includes a speaker and one or more processors programmed to implement a delayless subband filtered-x least mean square control algorithm. The algorithm includes a variable bandwidth discrete Fourier transform filter bank having a number of subbands such that the system, in response to a broadband white noise reference signal indicative of road noise in the vehicle, exhibits a uniform gain spectrum across a frequency range defined by the subbands and partially cancels the road noise via output of the speaker.

What is claimed is: 
     
       1. An active noise control system for a vehicle comprising:
 speakers; 
 sensors configured to detect broadband white noise reference signals indicative of road noise; and 
 a processor including a delayless subband filtered-x least mean square control algorithm that comprises a variable bandwidth discrete Fourier transform filter bank having a number of subbands, the processor configured to execute the delayless subband filtered-x least mean square control algorithm to process the broadband white noise reference signals and generate output exhibiting uniform gain spectrum across a frequency range defined by the subbands to partially cancel the road noise via the speakers. 
 
     
     
       2. The system of  claim 1 , wherein the delayless subband filtered-x least mean square control algorithm further comprises a uniform filter bank and wherein center frequencies of the variable bandwidth discrete Fourier transform filter bank are offset from center frequencies of the uniform filter bank by one half a bandwidth of the uniform filter bank. 
     
     
       3. The system of  claim 2 , wherein a bandwidth of the variable bandwidth discrete Fourier transform filter bank is less than the bandwidth of the uniform filter bank. 
     
     
       4. The system of  claim 2 , wherein a bandwidth of the variable bandwidth discrete Fourier transform filter bank is at least one half the bandwidth of the uniform filter bank. 
     
     
       5. A method for actively controlling noise in an active noise control (ANC) system comprising speakers, sensors, and one or more processors including a delayless subband filtered-x least mean square control algorithm that comprises a variable bandwidth discrete Fourier transform filter bank having a number of subbands, the method comprising:
 detecting by the sensors broadband white noise reference signals indicative of road noise and having an audible frequency range of 20 Hz to 20 kHz; and 
 executing by the one or more processors the delayless subband filtered-x least mean square control algorithm to process the broadband white noise reference signals, and generate output exhibiting uniform gain spectrum across a frequency range defined by the subbands to partially cancel the road noise via the speakers. 
 
     
     
       6. The method of  claim 5 , wherein the delayless subband filtered-x least mean square control algorithm further comprises a uniform filter bank and wherein center frequencies of the variable bandwidth discrete Fourier transform filter bank are offset from center frequencies of the uniform filter bank by one half a bandwidth of the uniform filter bank. 
     
     
       7. The method of  claim 6 , wherein a bandwidth of the variable bandwidth discrete Fourier transform filter bank is less than the bandwidth of the uniform filter bank. 
     
     
       8. The method of  claim 7 , wherein a bandwidth of the variable bandwidth discrete Fourier transform filter bank is at least one half the bandwidth of the uniform filter bank. 
     
     
       9. An active noise control (ANC) system comprising:
 a speaker; 
 sensors configured to detect broadband white noise reference signals indicative of road noise; and 
 one or more processors including a delayless subband filtered-x least mean square control algorithm that comprises a variable bandwidth discrete Fourier transform filter bank having a number of subbands, the one or more processors being configured to execute the delayless subband filtered-x least mean square control algorithm to process the broadband white noise reference signals and generate output exhibiting uniform gain spectrum across a frequency range defined by the subbands to partially cancel the road noise via the speakers. 
 
     
     
       10. The system of  claim 9 , wherein the delayless subband filtered-x least mean square control algorithm further comprises a uniform filter bank and wherein center frequencies of the variable bandwidth discrete Fourier transform filter bank are offset from center frequencies of the uniform filter bank by one half a bandwidth of the uniform filter bank. 
     
     
       11. The system of  claim 10 , wherein a bandwidth of the variable bandwidth discrete Fourier transform filter bank is less than the bandwidth of the uniform filter bank. 
     
     
       12. The system of  claim 10 , wherein a bandwidth of the variable bandwidth discrete Fourier transform filter bank is at least one half the bandwidth of the uniform filter bank.